1. Field of the Invention
This invention relates to improvements to hydrofoil craft and particularly to an improved forward strut connection which will predictably fail on predetermined impact and separate from the vessel in a controlled manner along a predetermined arcuate path.
2. Description of the Prior Art
Hydrofoil crafts are waterborne vessels which can move through water in a hull-borne mode similar to a conventional boat and in a foil-borne mode wherein the hull is carried above the water supported on foils which depend from the hull and extend generally horizontally to the surface of the water and develop lift forces in the water similar to those developed by airplane wings in air. The hydrofoil craft foils are carried on struts which are secured to the frame of the vessel and extend downwardly, generally vertically, during the foil-borne operation of the craft. During hull-borne operation of the craft, the struts are pivoted forwardly or aftwardly in most cases for protection of the water foil and to reduce water resistance of the strut and foil assembly.
When the hydrofoil craft is operated in its foil-borne mode, the vessel develops extremely high speed in comparison to conventional ship speeds. At these high speeds, safety problems arise because of the possibility that the rapidly moving strut and foil will strike large debris or other floating or submerged articles such as large driftwood, large animals such as whales, large mantas and the like, or other floating or submerged objects. Such impacts, occurring at the high speeds of hydrofoil craft operation, can cause serious damage to the hull of the hydrofoil craft and to the strut and foil assembly. The shock of rapid deceleration of the hydrofoil craft may be dangerous to passengers and crew members on board the craft. Serious structural damage may occur to the frame of the hull. If the strut and foil assembly is damaged, the hydrofoil craft can continue its voyage as a water-borne vessel and can be repaired at the end of the voyage.
In the U.S. Pat. No. 3,910,215, the forward hydrofoil strut is restrained in its foil-borne position by a mechanical support which is designed to rupture upon predetermined impact loads to permit the strut and foil assembly to pivot about the normal retraction pivot axis and assume rotation to a position which is opposite that of the water-borne mode. The aftward rotation of the foil, however, alters the lifting pressure and in fact reverses the lifting pressure causing a downward pressure to be applied to the hull of the hydrofoil craft. The downward pressure results in rapid accelerations and displacements with respect to the passengers and crew members.
In order to assure positive and certain release of the foil and strut assembly before any damaging stresses are applied to the hydrofoil hull, several designs have employed a pyrotechnic device which detonates and severs the strut when the strut experiences a pre-established impact. However, such detonation devices have not proved to be popular.
Thus there exists a need in hydrofoil craft development for a positive means for separating the forward strut and foil assembly of a hydrofoil craft from the hull before any damaging energy can be absorbed by the craft and its occupants, and for a controlled separation path for the strut as it separates from the craft.